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Vol.60, No.7, 489 ~ 502, 2022
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| Title |
| A Study on the Interrelationship between the Microstructural Features and the Elevated Temperature Strength of Multicomponent Al-Si-Cu-Ni Casting Alloys |
| 조민수 Min-su Jo , 조영희 Young-hee Cho , 이정무 Jung-moo Lee , 김수배 Soo-bae Kim , 김수현 Su-hyeon Kim , 장재일 Jae-il Jang |
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| Abstract |
| The elevated temperature strength of multicomponent Al-Si alloys is greatly affected by the volume fraction and the interconnectivity of hard phases formed upon solidification. In the present investigation, such influences were examined for two Al-Si-Cu-Ni alloys with different total volume fractions of hard phases. To control the microstructural features related to the size of the phase, the specimens were prepared with and without ultrasonic melt treatment (UST) at different cooling rates. The microstructures of the alloys were composed of primary Si, eutectic Si, (Al,Si)3(Zr,Ni,Fe), Al9FeNi and Al3(Cu,Ni)2 phases. The microstructural features, such as the size and aspect ratio of each phase, changed with UST and cooling rate, and accordingly, the elevated temperature strength at 350 ℃ was changed. The alloy with a high volume fraction of about 30 vol.% exhibited increased elevated temperature strength at 350 ℃ when ultrasonic melt treated, and the alloy having a volume fraction as low as about 18 vol.% exhibited the opposite results. Considering the microstructural features of the multi-component Al-Si alloy, a hexagonal shear-lag model was suggested, based on the well-known shearlag model proposed by Nardone and Prewo (Scr. Metall. 20;1986:43-48). Using the 2-D microstructural factors such as the size, aspect ratio of the phase and secondary dendrite arm spacing, the elevated temperature strength was calculated and compared with the measured value. Based on the hexagonal shear-lag model, the influence of microstructural factors on the elevated temperature strength was discussed for multi-component Al-Si-Cu-Ni alloys.
(Received 4 November, 2021; Accepted 12 April, 2022) |
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| Key Words |
| Al-Si-Cu-Ni alloy, elevated temperature strength, interconnectivity, microstructure, ultrasonic melt treatment, cooling rate |
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